Method of controlling the stabilizer content of cellulosic colloids



GEORGE ROCKER, 0F WILMINGTON, DELAWARE, ASSIGNOR TO E. I. DU JPONT DE NEMOURS & COMPANY, DELAWARE.

OF WILMINGTON, DELAWARE, A CORPORATION ()1? METHOD OF CONTROLLING THE STABILIZER CONTENT OF CELLULOSIC COLLOIDS.

No Drawing.

To all whom it may concern Be it known that I, GEORGE ROCKER, a citizen of the United States, and a resident of Wilmington, in the county of New Castle and State of Delaware, have invented a certain new and useful Method of Controlling the Stabilizer Content of C'ellulosic Colloids, of which the following is a specification.

This invention relates to the treatment of cellulosic colloids and has more particular reference to a method of treating cellulosic colloids to control the stabilizer content thereof, either to add stabilizer to the colloid being treated, or to overcome and ofiset extraction of stabilizer from the colloid during treatment with a solvent for the stabilizer.- In this latter mentioned aspect the method finds a particularly advantageous application when used in connection with a method whereby ethyl ether used for colloiding is extracted from nitrocellulose powder by washing with ethyl alcohol, the method of this invention providing for the retention in the powder, during the said Washing, of the desired and previously introduced stabilizer, despite the fact that alcohol is a solvent for the stabilizer, e. g. diphenylamine. Since the method finds advantageous application in the art of manufacturing nitrocellulose powder I- describe it with more particular reference to that art, but do not confine it thereto, nor to the treatment of nitrocellulose colloids.

I have discovered that a stabilizer, for example, diphenylamine, can be added to nitrocellulose powder by treating the powder with a solution of the stabilizer, as, for example, an ethyl alcohol solution, and have also discovered that the stabilizer content of powder may be held constant during washing with a volatile solvent for the stabilizer,

e. g. ethyl alcohol, provided stabilizer be added to the solvent in an amount sufficient to give equilibrium between the stabilizer in the "powder and that in the solvent. The present method is based upon these discoveries. y H

In working with diphenylamine as a stabilizer various strengths of alcohol may be used. As I prefer to use 60% or 80% of alcohol by volume (alcohol-water solution) ll refer more particularly to these strengths and confine my examples, etc., to them; but

Specification of Letters Patent.

Patented Aug. i, 192 2.,

Application filed December 17, 1920. Serial No. 431,396.

as will be evident, the method may be carried out with other strengths of alcohol, and, indeed, with other stabilizers, for example dinitrotoluol, and other solvents.

With 60% alcohol, my experiments show that for either adding diphenylamine to the powder, or for holding in the powder during the washing, the diphenylamine previously added thereto, the necessary percentage (y) of diphenylamine in the alcohol is given by the formula:

where X: of diphenylamine desired in thefinished powder, and B:%ofdiphenylamine already in the owder, this latter percentage being on a nished powder basis, 1. e.

weight of diphenylamine and B, for any values above .25 is to be taken as a constant, .25, since I have found that, for practical purposes, diphenylaminefree 80% alcohol will, by extraction, reduce greater than 25%, of diphenylamine in the powder down to 25%, but will not reduce it below that percent. 7

As will appear from the specific examples given hereinafter, it is not generally neces sary that the calculated amount be exactly alhered to, since small departures therefro are permissible in practical work.

Intreating powder to add thereto sufi cient diphenylamine to give a desired specified percentage it is desirable towash the powder, with the aid of anysuitable device having provisions for continuous infiowand outflow, with a flow of alcohol containing the calculated percentage of diphenylamine centage in the powder, until test of the offflowing alcohol shows that no diphenylamine has been lost by the alcohol in its passage through the powder, continuously introduced fresh alcohol, containing the calculated percentage of diphenylamine, being of course used for the washing. With the alcohol losing no diphenylamine in its passage, of course no more diphenylamine is being added to the powder; but alcohol containing the calculated percentage of dis phenylamine will add di henylamine to the powder up to the speci ed percentagegfso that, with the condition of no-diphenylamine-lost'reached, the specified percentage of diphenylamine has been added; further washing, with alcohol of the calculated percentage has no effect on the specified percentage of diphenylamine in the powder, as alcohol containing the calculated percentage of diphenylamine gives equilibrium at the specified percentage.

The diphenylamine having been added to the powder, the alcohol 4 is next removed from the powder, this being preferably done by first draining the alcohol from the powder and then washing with a liquid with which the alcohol is miscible but which is not a solvent for diphenylamine, e. g. water. As will be understood by those skilled in the art there should be used, of the solution of calculated diphenylamine strength, a quantity in excess of that containing merely the total weight of diphenylamine that it is de sired to add to the batch of powder since the entire content of diphenylamine in the solution will not be transferred to the powder; the excess desirable will of course vary with the particular powder being treated.

As examples of increasing the diphenylamine content of powder I have, usin alcohol containing 6 pounds of dip enylamine per 10,000 pounds of solution, raised the diphenylamine content of'the powder from substantially 5% up to .65%; and using 80% alcohol containing 19 pounds of diphenylamine per 10,000 pounds of solution I have raised the diphenylamine content of the powder from substantially ..5% up to .7 5%.

. As previously indicated, the method may be applied particularly advantageously when used in conjunction with that method, for removing ethyl ether and ethyl alcohol .solvent from nitrocellulose powder, which comprises first washing with ethyl alcohol to remove the ether, except for that corresponding to the desired residual solvent, dra ning the alcohol from the powder and with water to-remove the althen washin cohol; for addition of the diphenylamine to the alcohol used for washing out the ether fos revents the extraction of thediphenylamme contained in the powder. As examples of this use of the, method in the retaining of stabilizer, I have proceeded as described below, with satisfactory results In washin reen nitrocellulose powder with 60% alcohol, the powder containing substantially .5% of diphenylamine, i. e. containing a weight of diphenylamine equal to substantially .5% of the weight of the corresponding dry or finished powder, 3 to 4 pounds of diphenylamine to each 10,000 pounds ofisolution gives the necessary equilibrium and preserves the diphenylamine content at substantially 5%. I

In washing green? powder containing substantially 5% of diphenylamine (dry powder basis) with 80% alcohol, 10 to 11 pounds of diphenylamine to each 10,000 pounds of solution gives the necessary equilibrium. 1

As previously stated, the method may be practiced with alcoholic solutions of other strengths. So far as I am aware the curves obtained by plotting percentage of diphenylamine in the finished powder against the corresponding experimentally determined values of percent of diphenylamine in the alcohol, in the usual way, are straight lines. The formulas will be similar to those given above, the value of B being the percent at which the curve meets the percent in powder axis, shown by the plot.

I claim:

1. The method of controlling the stabilizer content of a cellulosic colloid which comprises washing the colloid in a volatile 100 solvent containing the stabilizer. A

2. The method of controlling the stabilizer content of a cellulosic colloid which comprises washing the colloid with a solution containing the stabilizer, and then washing the colloid in a liquid in which the solvent of the stabilizer is miscible and the stabilizer is insoluble.

3. The method of controlling the stabilizer content of a stabilizer-containing cellulosic colloid during washing with a volatile liqluid in which the stabilizer is soluble,

w ich comprises adding to the washing liquid an amount of stabilizer sufiicient to ive equilibrium. between the colloid-contained stabilizer and. that in the washing liquid.

4. The method of controlling the stabilizer content of a stabilizer-containing cellulosic colloid during washing with a liquid in which the stabilizer is soluble, which comprises adding to the washing liquid an amount of stabilizer in ex essof thatsufiicient to give equilibrium between the colloid-contained stabilizer and that in the washing liquid,'and then treating to remove the washing liquid while leaving the stabilizer in the colloid.

5. The method of controlling the diphenylamine content of a cellulosic colloid during washing with ethyl alcohol which comprises adding diphenylamine to the alcohol.

6. The method of controlling the diphenylamine content of a cellulosic colloid which comprises washing with a substantially 60% solution of ethyl alcohol containing a percentage of diphenylamine determined in substantial accordance with the formula,

wherein Xzper cent of di henylamine desired in the finished pow er, and Bzper cent of diphenylamine already in the powder, this per cent B, for any values above that percentage below which diphenylamine-free 60% alcohol will not reduce the diphenylamine content of the colloid, to be taken as that percentage.

7. The method of controlling the diphenylamine content ofv a cellulosic colloid which comprises washing with a substantially 60% solution of ethyl alcohol containing a percentage of diphenylamine determined in substantial accordance with the formula,-

wherein X=per cent of diphenylamine dea sired in the finished powder, and B =per cent of diphenylamine already in the owder, this per cent B, for any values a ove .37, to be taken as .37.

8. The method of controlling the diphenylamine content of a cellulosic colloid during washing with substantially 60% ethyl alcohol, which comprises adding diphenylamine to the alcohol in substantially the proportion of 3 to 4 pounds of diphenylamme to 10,000pounds of alcohol.

9. The method of recovering ethyl alcohol and ethyl ether solvent from a nitrocellulose colloid containing a stabilizer soluble in ethyl alcohol, which comprises washing the colloid with ethyl alcohol containing stabilizer until the ether is sufficiently removed, draining alcohol from the colloid and then washing with water.

10. The method of removing ethyl alcohol and eth l ether solvent from a nitrocellulose collold containing substantially .5%

of'diphenylamine, which comprises Washing the colloid in substantially 60% ethyl alcohol containing diphenylamine in substantially the proportion of 3 to 4 pounds of diphenylamine to 10,000 pounds of alcohol, until the ether is sufliciently removed, draining alcohol from the colloid and then washin with water.

n testimony whereof I afiix my si nature.

GEORGE ROC ER. 

